Spherical UV mapping is in:
blender/source/blender/src/editface.c :
You can add it back in by adding:
MENUSTRING("Spherical map", UV_SPHERE_MAPPING)
to the:
mode= pupmenu(MENUTITLE("UV Calculation")
section.
The case for spherical is combined with the cylinder mapping:
case UV_SPHERE_MAPPING:
case UV_CYL_MAPPING:
and uses if else statements to determine which function to call. It does give so so results but is better that trying to use the other mapping methods to apply a texture to a sphere.
For the adventurous, the code for spherical mapping is in:
source/blender/blenkernel/intern/texture.c:
spheremap(float x, float y, float z, float *adr1, float *adr2)